The present invention relates to the Oppenauer oxidation of primary allylic alcohols to their corresponding aldehydes. The invention is particularly applicable to the Oppenauer oxidation of 3-substituted and 3,3-disubstituted allyl alcohols, and will be described primarily with respect to the Oppenauer oxidation of geraniol (trans) and nerol (cis)(3,7-dimethyl-2,6-octadien-1-ol) to citral (3,7-dimethyl-2,6-octadienal), although it will be apparent to those skilled in the art that the present invention has other applications.
Citral which is a mixture of citral-a (geranial) and citral-b (neral) is a highly useful intermediate in the syntheses of several desirable products. The syntheses of ionones and methyl ionones begin with citral. It may be converted via a condensation with acetone, directly to pseudoionone, which in turn can be converted into .alpha.-ionone and .beta.-ionone. The latter is a key intermediate in the production of Vitamin A. Pseudoionone is useful in the production of Vitamin E. Citral has many other uses, for instance, in synthetic flavors.